Indian Philosophy: Orthodox and Heterodox Schools

Indian Philosophy or Hindu Philosophy is generally classified into 6 orthodox schools (āstika) and 3 heterodox (nāstika) schools. The basic difference between the two branches of Hindu Philosophy schools is said to be based on the recognition of Vedas. Orthodox schools recognize the authority of Vedas while heterodox schools don’t believe in the authority of Vedas. Out of these nine systems eight are atheistic as there is no place for God in them. Only Uttara Mimansa, which is also called Vedanta, has a place for God in it.

Six Orthodox Schools (Classical Schools) of Indian Philosophy

The 6 classical schools (shatdarshan) are Sankhya, Yoga, Nyaya, Vaisheshik, Purva Mimansa and Uttar Mimansa (Vedanta). Almost all Indian schools of thought accepted the theory of karma and rebirth, and the ideal of moksha is conceived as liberation from the cycle of births and deaths. Moksha/liberation is considered as the highest goal of human struggle.

Sankhya Philosophy

Sankhya is the oldest philosphy. It was put forward by Kapila. Sankhya philosophy provided the materialistic ontology for Nyaya and Vaisheshik, but there is very little original literature in Sankhya. It is generally believed that Sankhya Philosophy is dualistic and not monistic because it has two entities, purush (spirit) and prakriti (nature) in it. Samkhya emphasizes the attainment of knowledge of self by means of concentration and meditation. Sankhya holds that it is the self-knowledge that leads to liberation and not any exterior influence or agent. Samkhya forms the philosophical basis for Yoga. In Samkhya, the necessity of God is not felt for epistemological clarity about the interrelationship between higher Self, individual self, and the universe around us.

Purush vs Prakriti: In the beginning the philosophy was materialistic as it talked only about Prakrithi, but later the element of purush was also added to it. While Purusha is posited as the only sentient being, ever existent, and immaterial, Prakriti is said to be the material basis of this universe, composed of three basic elements (Gunas) – namely Tamas, Rajas, and Sattva.

Yoga Philosophy


Yoga presents a method of physical and mental discipline. The Yoga presents a practical path for the realization of the self whereas the Samkhya emphasizes the attainment of knowledge of self by means of concentration and meditation. Releasing Purush from Parkriti by means of physical and mental discipline is the concept behind Yoga.

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Founder of Yoga is Pathanjai. Yoga does not require belief in God, although such a belief is accepted as help in initial stage of mental concentration and control of mind.

Nyaya Philosophy

Nyaya Philosophy states that nothing is acceptable unless it is in accordance with reason and experience (scientific approach). Founder of this philosophy is Gautam and the principles are mentioned in Nyaya Sutras. Nyaya says that the world is real and the philosophy does not follow a monist view.

Nyaya philosophy relies on several pramanas i.e. means of obtaining true knowledge as its epistemology. According to it, the pradhan pramana or principal means of obtaining knowledge is pratyaksha pramana i.e. the knowledge obtained through the 5 senses. There are also other pramanas like anumana (inference, through which we can obtain true knowledge) and shabda pramana (a statement of an expert).

NB: Subsequent philosophers who claimed to be Nyayiks, e.g. Vatsyayan (who wrote Nyaya Bhashya), Udayan (who wrote Kusumanjali) etc. distorted the Nyaya philosophy by introducing theological elements in it. Navya Nyaya scholars like Gangesh resorted to gymnasics in logic.

Vaisheshik Philosophy

The classical Indian philosophy Vaisheshik, was the physics of ancient times. It propounded the atomic theory of its founder Kannada. At one time Vaisheshik was regarded as part of the Nyaya philosophy, since physics is part of science. But since physics is the most fundamental of all sciences, Vaisheshik was later separated from Nyaya and put forth as a separate philosophy. To make it short, Vaisheshik is a realistic and objective philosophy of universe.

Purva mimansa (mimansa)

The word Mimamsa means to analyze and understand thoroughly.  Purva Mimamsa examines the teachings of the Veda in the light of karma-kanda rituals, ie karma-mimamsa system is called purva-mimamsa. Purva mimansa (or briefly mimansa) lays emphasis on the performance of the yagya for attaining various spiritual and worldly benefits.  Hence this philosophy relies on the Brahmana (and samhita) part of the Vedas.

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Uttara Mimamsa (Vedanda)

Vedanta says that the world is unreal, Maya. Vedanta is monistic, in other words, it says that there is only one reality, Brahman. Vedanta lays emphasis on brahmagyan, hence relies on the Upanishad part of the Vedas. Vedanda has its roots in Sankya Philosophy.

There are three sub-branhces for Vedanda :

  1. Absolute Monism of Shankara
  2. Vishishtha Advaita or qualified monism of Ramanuja
  3. Dvaita of Madhva

PS: A close examination shows that the first 4 classical systems are not entirely based on Vedas. But last two, the Purva Mimansa and the Uttar Mimansa, certainly rely on the Vedas.

Three Heterodox Schools of Indian Philosophy

Schools that do not accept the authority of vedas are by definition unorthodox (nastika) systems. The following schools belongs to heterodox schools of Indian Philosophy.


It is characterised as materialistic and aesthetic school of thought. Accepted direct perception as the surest method to prove the truth of anything. Insists on joyful living. Also known as Lokayata, Carvaka is a materialistic school of thought. Its founder was Carvaka, author of the Barhaspatya Sutras in the final centuries B.C. The original texts have been lost and our understanding of them is based largely on criticism of the ideas by other schools. As early as the 5th Century, Saddaniti and Buddhaghosa connected the Lokayatas with the Vitandas (or Sophists), and the term Carvaka was first recorded in the 7th Century by the philosopher Purandara, and in the 8th Century by Kamalasila and Haribhadra.

Buddhist Philosophy


It is a system of beliefs based on the teachings of Siddhartha Gautma. Buddhism is a non-theistic philosophy whose tenets are not especially concerned with the existence or non-existence of God. Four Noble Truths in Buddhism are the following.

  1. There is suffering
  2. There is cause of suffering
  3. There is cessation of suffering
  4. There is a way to cessation of suffering
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Buddhists philosophy of life to get ‘Nirvana’ from suffering is based on the following eight principles:

  1. Right Faith (Samyak Dristi)
  2. Right Resolve (Samyak Sankalpa)
  3. Right Speech (Samyak Vakya)
  4. Right Action (Samyak Karmanta)
  5. Right Living ( Samyak Ajiva)
  6. Right Thought (Samyak Smriti)
  7. Right concentration (Samyak Samadhi)
  8. Right Effort (Samyak Vyayama)

Jain Philosophy

Already in existence by 6th century B.C , it was revived by Mahavira, the 24th Jain Tirhthankar. According to Jainism Nirvana or liberation is obtained through three jewels: Right Philosophy, Right Knowledge and Right Conduct (Tri-ratna). Right conduct implies 5 absinences: not to lie, not to steal, not to strive for luxury and not to strive for possessions, not to be unchaste and not to injure (Ahimsa).

Ajivika Philosophy

A related philosophy which some classify under the heterodox sytem is Ajivika Philosophy. The Ājīvikas may simply have been a more loosely-organized group of wandering ascetics (shramanas or sannyasins). Some of its prominent figures were Makkhali Gosala and Sanjaya Belatthaputta. This was an ascetic movement of the Mahajanapada period in the Indian subcontinent.


  1. International Forum for Neovedantins.
  2. Philosophy basics.

UPSC Questions related to Hindu Philosophy

Qn: With reference to the history of philosophical thought in India, consider the following statements regarding Sankhya school: (2013 CSE Prelims)

  1. Sankhya does not accept the theory of rebirth or transmigration of soul.
  2. Sankhya holds that it is the self-knowledge that leads to liberation and not any exterior influence or agent.

Which of the statements given above is /are correct?

A – 1only
B – 2 only
C – Both 1 and 2
D – Neither 1 nor 2

Ans : B – 2 only

Qn. Which one of the following pairs does not form part of the six systems of Indian Philosophy? (2014 CSE Prelims)

A – Mimamsa and Vedanta
B – Nyaya and Vaisheshika
C – Lokayata and Kapalika
D – Sankhya and Yoga

Ans C – Lokayata and Kapalika.

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